As a marketing case study, Glass has been an act of genius. From the moment Glass was announced it was positioned as the must-have accessory for the new class of daredevil entrepreneurs. When a Glass wearer wasn’t solving the world's hardest problems, he was jumping out of airplanes or strutting down a fashion runway flanked by supermodels.

The message wasn't subtle, but it was effective: With Glass, you could feel like just like James Bond.

Except you couldn't. Because Glass wasn't available to just anyone. You had to be invited to buy Glass. You had to worthy of wearing it. You had to emotionally commit before Google would consent to take your money. Would-be Glass wearers who hadn't attended the Google developer conference in 2012 had to pledge their enthusiasm before the entire Twitterverse.

This approach practically guaranteed Google good reviews when Glass finally shipped this spring. It's hard to say a product sucks after you've paid $1631 for it, especially knowing that you were hand-picked to try the experimental version.

Yet amid all the proclamations about how amazing and cool Glass is, there's enough grumbling about everything from quality of sound to ease of use to indicate that Glass needs a significant upgrade if it is going to catch on with mainstream gadget buyers.

Here are the biggest problems:

Sound quality makes Glass a poor communications device. As Bridget Carey, a reporter at CNET, observes when she tried to use Glass to receive remote coaching at an archery range, the speaker "wasn't loud enough to overpower the few people talking in the room." The fact you can't hear people talk on Glass if you are in a public place makes it highly unlikely that Glass will become an iPhone killer or even a popular Android accessory.

Glass easily gets cluttered. This won't come as a surprise to people who have bought into the Google ecosystem. Organizational hierarchy has never ranked high in Google's UX. Part of Gmail's beauty was it didn't require you to create an elaborate filing system in order to retrieve an email. You could just dump everything into an archive. Glass is the same way—photos, videos, emails and notifications all get deposited in an area known as "the timeline." This method works great until entropy sets in.

Glass doesn't invite prolonged interaction. Glass has two main input mechanisms. You can navigate the timeline by swiping or tapping the touchpad on the armpiece or you can speak a voice command by prefacing it with the phrase "Ok Glass" as in "Ok Glass, take a picture" or "Ok Glass, send an email to Brenda." "Unfortunately, it's easy to misspeak and watch Glass eagerly perform the wrong command," observes Paul Miller of The Verge. And if voice input was awkward for Miller, using the touchpad was even more painful. "We've accidentally tapped to share a photo with the wrong Google+ contact a dozen times, simply because Glass registers a tap instead of a swipe," he writes.

Glass apps quickly lead to information overload. The first apps released on Glass have all been about pushing everything from news headlines to Twitter updates to the person wearing Glass. The problem with notifications, as Loic Le Meur, a well-known tech personality discovered on Tuesday, is they quickly become an annoying distraction if they are not properly filtered. "Anyone know how to filter the notifications from new Tweets in Google Glass Twitter app?" he asks on Twitter. "My Glass is getting notified every 10 seconds!!!!" [Note: as Loic responds in the comments, he figured out how to tweak his settings and now loves receiving customized alerts.]

The Glass camera lacks basic camera functionality. People are used to cameras on smartphone constantly improving. Glass bucks this trend. There are no settings of any kind and no live preview, so each shot is composed blindly. "After using Glass for the past few days now and taking hundreds of photos, I've gotten used to it," writes Chris Chavez of Phandroid. "The camera shoots at a downward angle meaning you point your nose at what you want in the center (if that makes sense)." It does, but only if you are particular kind of gadget-loving masochist.

Given Glass's limitations it seems like it’s only a matter of time before Google either releases a radically improved version of the product, or the hype plays itself out and Glass becomes a victim of its marketing success. Will Glass go down in history as one of the decade's most innovative products or one of its biggest marketing flops? Today, either outcome seems equally possible.